1. Field of the Invention
The present invention relates to technology for printing by forming dots on a printing medium while performing a main scan, and more particularly relates to technology to determine the adjustment value for correcting the misalignment of the dot recording positions in the main scanning direction.
2. Description of the Related Art
In recent years, as computer output devices, there has been a broad popularization of printers of the type that eject ink from a head. Among this type of color printer, there are printers that print an image by forming dots on a printing medium by ejecting ink drops from a nozzle while performing a main scan in both the forward and reverse scanning passes.
In a printer in which dots are formed on a printing medium through the ejection of ink droplets from nozzles, dot recording position misalignment can occur due to deviation of the direction in which ink droplets are ejected, backlash of the driving mechanism in the main scanning direction, and warping of the platen that supports the printing medium from below. As a technology to resolve this position misalignment, the technology disclosed by the inventors in Japanese application JPA 5-69625 is known. In this conventional technology, the adjustment value used to eliminate the dot formation position misalignment in the main scanning direction are preset, and the recording positions in the forward and reverse scanning passes are corrected based on the adjustment value.
However, in the conventional adjustment value determination method, the adjustment value must be determined by the user based on observation of the printing results, and the adjustment value cannot be automatically determined.
Accordingly, an object of the present invention is to automatically carry out determination of the adjustment value to adjust recording position misalignment in the main scanning direction when printing is performed in which dots are formed on a printing medium through the ejection of ink droplets from nozzles.
In order to resolve at least a part of the problem described above, the present invention executes prescribed processing using a printing apparatus having a print head with nozzles. This printing apparatus includes a print head having nozzles that eject ink droplets; an inspection unit that optically detects the passage of ink droplets ejected from one of the nozzles; a head driving unit that drives the nozzles to eject ink droplets; a main scanning driving unit that performs main scanning in which the print head is moved relative to the inspection unit; a timer; and a controller that controls the print head, the inspection unit, the head driving unit, the main scanning driving unit and the timer.
In the printing apparatus described above, a forward pass test is performed in which ink droplets are detected using the inspection unit while ejecting ink droplets from one of the nozzles and moving the print head along the forward pass of main scanning. A reverse pass test is performed in which ink droplets are detected using the inspection unit while ejecting ink droplets from one of the nozzles and moving the print head along the reverse pass of main scanning. The adjustment value is then determined based on the results of the forward pass test and the reverse pass test. According to this aspect, the adjustment value of the dot formation position misalignment can be automatically determined without the need for human visual review.
It is preferable to identify a detection time tfp at which the ink droplets were detected by the inspection unit in the forward pass test. It is also preferable to identify a detection time tbp at which the ink droplets were detected by the inspection unit in the reverse pass test. The adjustment value is then preferably determined using the detection time tfp and the detection time tbp. According to this aspect, the dot formation position misalignment adjustment value can be calculated based on the measurement values tfp and tbp.
It is preferable that the adjustment value is calculated based on the following values: a reference eject time tf0 of the ink droplet is to be identified by the inspection unit in the forward pass test under a reference condition of the dot formation position misalignment adjustment; a reference eject time tb0 of the ink droplet is to be identified by the inspection unit in the reverse pass test under the reference condition; the detection time tfp, and tbp; a distance HP between a particular nozzle and a surface of the printing medium when the particular nozzle is positioned facing the printing medium; and an ink droplet velocity component Vk in a direction connecting a nozzle to be inspected and a detection position of the inspection unit when the nozzle to be inspected is closest to the detection position. According to this aspect, the adjustment value can be determined based on the predetermined values and the measurement values obtained in the forward pass test and the reverse pass test.
It is preferable to identify a position Pfp of the nozzle at the detection time tfp in the forward pass test. It is also preferable to identify a position Pbp of the nozzle at the detection time tbp in the reverse pass test. The adjustment value is then determined using the position Pfp and the position Pbp. According to this aspect, the dot formation position misalignment adjustment value can also be calculated based on the measurement values Pfp and Pbp.
In the determination of the adjustment value, it is preferable that the adjustment value calculated based on following values: a reference position Pf0 at which the nozzle ejects the ink droplet that is to be identified by the inspection unit in the forward pass test under a reference condition of the dot formation position misalignment adjustment; a reference position Pb0 at which the nozzle ejects the ink droplet that is to be identified by the inspection unit in the reverse pass test under the reference condition; the position Pfp, and Pbp; a distance HP between a particular nozzle and a surface of the printing medium when the particular nozzle is positioned facing the printing medium; the shortest distance HL between the nozzle and detection position of the inspection unit; an ink droplet velocity component Vk in a direction connecting the nozzle and the detection position when the nozzle is closest to the detection position; and the relative velocity Vc of the print head relative to the printing medium during the main scanning. According to this aspect, the adjustment value can be determined based on the predetermined values and the measurement values obtained in the forward pass test and the reverse pass test.
The present invention can be implemented in the various forms indicated below.
(1) Adjustment value determination method, printing method, print control method
(2) Printing apparatus, print control apparatus
(3) Computer program to implement the above apparatuses and methods
(4) Recording medium on which is recorded the computer program to implement the above apparatuses and methods
(5) Data signals that are embodied in transmission waves, including the computer program to implement the above apparatuses and methods
These and other objects, features, aspects, and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with the accompanying drawings.